Isotropic sensor 1, which comprises three sensor units 2, provided with a lead wire winding 3 surrounded by a conducting screen 4, the screen 4 being interrupted in two first zones I1, I2 diametrically opposite, there being in one of said zones I1, I2 the terminals VB for measuring the currents induced, wherein the two ends of each screen segment 41, 42 in the first two zones I1, I2 are connected two by two by means of conductors 5, 6 and comprises two second zones I3, I4 of interruption disposed at a halfway point of each screen segment 41, 42, in such a way that it is possible to measure at high frequencies simultaneously, independently and with precision, both magnetic field B and electric field E.